The invention relates to detection and imaging, and more particularly to systems and methods for optical detection and imaging of sample arrays.
Surface plasmon resonance (SPR) detection is an optical detection technique that is used to detect molecular adsorptions and interactions. The SPR detection is used in a wide variety of chemical systems, including biosensors. Typically, SPR sensors comprise an arrangement where a prism supports a thin metal layer. A ligand molecule is immobilized on one side of the thin metal layer to form a modified metal surface from the thin metal layer. A sample is disposed on the modified metal surface. A light beam incident on the sample excites surface plasmons in the thin metal layer in a resonant manner. The surface plasmons propagate in a direction parallel to the interface formed between the thin metal layer and the prism (metal/prism interface). Since the surface plasmons are present at the boundary of the thin metal layer and an external medium (e.g., air or water), the oscillations of the surface plasmons are responsive to any changes in the boundary of the metal and the external medium, such as the adsorption of molecules on the metal surface. SPR phenomenon is typically detected by sensing refractive index changes near the surface of the thin metal layer. A reflection spectrum of the modified metal surface may be determined by measuring the intensity of a reflected light as a function of an angle of incidence or a wavelength of the incident light. The sensitivity of the SPR phenomenon towards refractive index changes at the boundary is useful in observing and quantifying chemical reactions at a thin metal film/sample solution interface.
Typically, SPR systems use two different paths in an interferometer. A first path may be referred to as a reference arm and a second path may be referred to as a sample arm. The general direction from a radiation source towards a reference is referred to as a reference arm, and a general direction from the radiation source towards the sample is referred to as a sample arm. The incident light from the radiation source is split into two portions, a first portion travels through the reference arm and is incident on the reference sample, and the second portion travels through the sample path and is incident on the samples. Having two different paths in the interferometer makes the system susceptible to environmental factors, such as vibrations, resulting in noise in the detection and imaging. The SPR techniques in an interferometer configuration are relatively more sensitive to environmental factors such as vibrations and temperature fluctuations. The vibrations may cause misalignment between the two arms in the interferometer, which may result in lack in coherency of the light travelling through the two different paths, thus, affecting the sensitivity of the detection.
Therefore, it is desirable to have improved systems and methods for detecting and imaging of arrays of samples.